Ohio State University Extension Bulletin

Ohio Trees

Bulletin 700-00

Key to Classes, Groups, Subgroups, and Genera

Class A. Leaves are evergreen, needlelike, narrow-linear, awl-shaped, or scalelike.

Group I–Leaves in bundles are needlelike.

Group II–Leaves opposite and awl-shaped or scalelike. Leaves are small, often overlapping, and adpressed.

I. Leaves are sharp and harsh to the touch, especially on the main branches or older twigs. Leaves are free at the apex. Fruit is berrylike.

Juniperus–Juniper

II. Leaves are soft to the touch and scalelike. Most are closely adpressed to the branchlets. Fruit is a woody cone with six to 12 scales.

Thuja–Arborvitae

Group III–Leaves are alternate and scattered on the stem. Leaves are narrow and linear.

I. Winter buds on normal shoots are conspicuously long-pointed, brown with many scales, and non-resinous.

Pseudotsuga–Douglas-Fir

II. Buds are not long-pointed.

A. Leaves are deciduous at their base. Old twigs are not roughened by persistent leaf bases.

Abies–Fir

AA. Leaves are deciduous above the leaf base, leaving the twigs roughened by persistent leaf bases.

|. Leaves are flat and arranged into two planes. White, stomatic lines are present beneath the leaf. Twigs are only slightly roughened by persistent leaf bases.

Tsuga–Hemlock

||. Leaves are four-sided with stomatic lines of equal numbers on all sides. Twigs are strongly roughened by persistent leaf bases.

Picea–Spruce

Class B. Leaves are deciduous, mostly broad, and occasionally narrow or linear.

Group I–Leaves are opposite or whorled.

Subgroup I–Leaves are compound.

I. Leaves are palmately compound.

Aesculus–Buckeye, Horsechestnut

II. Leaves are pinnately compound.

A. Side buds are hidden.

Acer–Boxelder

AA. Side buds are prominent. Bundle scars are numerous.

Fraxinus–Ash

Subgroup II–Leaves are lobed.

I. Pith is chambered or sometimes hollow.

Paulownia–Paulownia

II. Pith is solid.

Acer–Maple

Subgroup III–Leaves are toothed.

I. Petioles are connected directly or by a line around the twig.

Viburnum–Viburnum

II. Petioles are not connected either directly or by a line around the twig.

Euonymus–Euonymus

Subgroup IV–Leaves are entire.

I. Pith is chambered or sometimes hollow.

Paulownia–Paulownia

II. Pith is solid.

A. Leaves are long-petioled, large (4—12 inches [10—301/2 cm] long), and often whorled.

Catalpa–Catalpa

AA. Leaves are not as above.

|. Bundle scars are almost in a complete circle. Side buds are globu- lar with four to five pairs of bud scales.

Chionanthus–Fringetree

||. Bundle scars and buds are not as above. Leaves have parallel veins.

Cornus–Dogwood

Group II–Leaves are alternate.

Subgroup I–Leaves are compound.

I. Leaves are twice compound.

A. Twigs are spiny or thorny.

|. Spines are unbranched, short, and stout.

Aralia–Aralia

||. Thorn is simple or branched, stout, and 2-4 or more inches in length.

Gleditsia–Honeylocust

AA. Twigs are not spiny or thorny.

Gymnocladus–Kentucky Coffeetree

II. Leaves are once compound.

A. Leaflets are trifoliate.

Ptelea–Hop Tree

AA. Leaflets are always more than three.

|. Leaflets are toothed.

a. Stems are thorny.

i. Plants have aromatic branches when crushed.

Zanthoxylum–Pricklyash

ii. Plants are without aromatic branches when crushed.

Gleditsia–Honeylocust

aa. Stems are not thorny.

i. Stipules are present, broad, and coarsely toothed.

Sorbus–Mountain-Ash

ii. Stipules are absent.

A) Pith is chambered.

Juglans–Butternut, Walnut

AA) Pith is solid.

|) Buds are naked or valvate.

a) Buds are naked.

Rhus–Sumac

aa) Buds are valvate.

Carya–Hickory

||) Buds have several overlapping scales.

Carya–Hickory

||. Leaflets are entire.

a. Stipules are absent or fall early. Side buds are visible.

i. Buds are naked.

Rhus–Sumac

ii. Buds are scaly.

Ailanthus –Tree of Heaven

aa. Stipules are present. Side buds are usually hidden by petiole bases or sunken beneath leaf scars.

Robinia–Locust

Subgroup II–Leaves are lobed.

I. Lobes are entire and not regularly toothed.

A. Buds are not clustered at the end of the twigs.

|. Leaves on 2-year-old twigs are borne mostly in clusters of three to five on spurs. Leaves are fan-shaped with parallel veins.

Ginkgo–Ginkgo

||. Leaves on 2-year-old twigs are not borne in clusters on spurs.

a. Stipular lines encircle the twig.

Liriodendron–Tuliptree

aa. Stipular lines are absent.

i. Branches and foliage are fragrant when crushed.

Sassafras–Sassafras

ii. Branches and foliage are not fragrant when crushed.

Populus–Poplar

AA. Buds are clustered at the ends of the twigs.

Quercus–Oak

II. Lobes are toothed.

A. Leaves are woolly or pubescent (hairy) beneath.

Populus–Poplar

AA. Leaves are not woolly or pubescent (hairy) beneath, except possibly on veins when young.

|. Buds are hidden by the base of the petiole. Terminal bud is lacking. Stipule scar extends around the stem.

Platanus–Planetree

||. Buds are not hidden by petiole base. Stipule scars are not encircling the twig.

a. Leaves are palmately veined and star-shaped. Older twigs usually have corky ridges.

Liquidambar–Sweetgum

aa. Leaves are pinnately veined and vary in shape from entire to mitten- shaped or lobed. Twigs are without corky ridges.

Morus–Mulberry

Subgroup III–Leaves are toothed.

I. Buds are valvate. Leaves are mostly narrow. Veins are reticulate (curving and connected by cross veins).

Salix–Willow

II. Buds have several overlapping scales.

A. Twigs are thorny.

Crataegus–Hawthorn

AA. Twigs are not thorny, but may have stiff, short, spurs.

|. Black glands (small, short, and threadlike) are present on midrib.

Malus–Crabapple

||. Black glands on the midrib are absent.

a. Veins are straight, parallel, and running to the teeth without much branching.

i. Outer bud scales number two to four, seldom five.

A) Winter catkins are present. Spur-like branches are present on 2- to 3-year-old twigs, each bearing two to three leaves. Leaves are crowded almost in a whorl.

Betula–Birch

AA) Winter catkins and spur-like branches are absent.

I) Leaves are two to three times as long as they are wide. Leaf margins are coarsely toothed and leaf tips are bristle-like.

Castanea–Chestnut

II) Leaves are nearly as wide as they are long. Leaf bases are usually heart-shaped or lopsided.

Tilia –Linden

ii. Outer bud scales number five or more.

A) Buds are clustered at the ends of the terminal twigs.

Quercus–Oak

AA) Buds are not clustered at the ends of the terminal twigs.

|) Buds are long-pointed with many scales. Leaves are either coarsely and singly toothed or simple with a wavy margin.

Fagus–Beech

||) Buds are smaller and more ovate with fewer scales. Leaves are finely and doubly toothed.

a) Leaves are rounded or heart-shaped at the base and rarely lopsided.

I] Bud scales are marked with fine, longitudinal lines. Leaves have each side vein forming one or two branches near the margin of the leaf.

Ostrya–Hophornbeam

II] Bud scales are without fine, longitudinal lines. Side veins are unbranched and run straight to the teeth.

Carpinus–Hornbeam

aa) Leaves are usually lopsided at the base.

Ulmus–Elm

aa. Veins are anastomosing, branching, and curving before reaching the margin of the leaf. (reticulate)

i. Leaf stalk is flattened vertically.

Populus–Poplar

ii. Leaf stalk is not flattened vertically but is round or nearly so.

A) Terminal bud is sticky and usually much larger than the side buds.

Populus–Poplar

AA) Terminal or pseudo-terminal bud is not sticky and usually not larger than the side buds.

|) Twigs have a bitter, almond taste.

Prunus–Plum, Cherry

||) Twigs do not have a bitter, almond taste.

a) Terminal buds are present.

I] Pith is diaphragmed or intermittently chambered. Leaves are prominently three-veined. Teeth are missing on lower third of the margin. Leaves are usually lopsided at the base.

Celtis–Hackberry

II] Pith is solid. Leaves are distinctly pinnately veined. Teeth are continued from base to tip or nearly so. Buds are long and pointed with four or five scales.